The present invention relates to therapeutic and prophylactic devices, and more particularly to devices for applying compressive pressures against a patient's limb.
It is known that the velocity of blood flow in a patient's extremities, particularly the legs, markedly decreases during confinement of the patient. Such pooling or stasis of blood is particularly pronounced during surgery, immediately after surgery, and when the patient has been confined to bed for extended periods of time. It is also known that stasis of blood is a significant cause leading to the formation of thrombi in the patient's extremities, which may have a severe deleterious effect on the patient, including death. Additionally, in certain patients it is desirable to move fluid out of interstitial spaces in extremity tissues, in order to reduce swelling associated with edema in the extremities.
Devices have been disclosed in U.S. Pat. Nos. 4,013,069 and 4,030,488, incorporated herein by reference, which develop and apply the desired compressive pressures against the patient's limbs. Such devices comprise a pair of sleeves which envelope the patient's limbs, and a controller for supplying fluid pressure to the sleeves. It has been found that the sleeves cause an uncomfortable build up of heat about the patient's limbs during extended use, since the sleeves essentially close the limbs from the atmosphere. One solution to this problem was proposed in U.S. Pat. No 4,091,804, incorporated herein by reference, through ventilation of the legs in the knee region. It is preferred that the air be distributed substantially throughout the length of the limbs. However, it has been found difficult to accomplish this result without excessive complication in the sleeve structure due to the size and volume needed for the compression chambers in the sleeve, and the multiple number of air supply lines apparently required at various locations on the sleeve.